1. Field of the Invention
The invention relates to a system for fastening a rail in place on a base and to a fastening for a rail which uses such a system.
2. Description of Related Art
When rails are to be fastened in place on which travel takes place with quite low loads and at quite low speeds, as is the case with tramways for example, the primary concerns are on the one hand wear which is as low as possible and on the other hand a comfortable ride and the minimising of emitted sounds. At the same time, such fastenings are also intended to be able to be fitted easily and to be able to be manufactured inexpensively.
In the rail fastenings which are used in practice, these requirements are met by mounting the rails on a solid base formed for example by a concrete sleeper or an isolated support made of concrete, with an elastic layer having a defined ability to yield being arranged between the foot of the rail and the solid base. The ability to yield of the elastic layer is selected in this case in such a way that, when travel takes place along the rail, the behaviour of the rail in the region of the given fastening is the same as it is in the unsupported region between two fastenings which is spanned by the rail in an unfastened state.
In the case of rail fastenings of this kind, the job of the fastening is to secure the rail in position in the horizontal direction at right angles to the longitudinal extent thereof and to prevent the rail from lifting away from the elastic layer in the vertical direction.
In a rail fastening system which is known from DE 198 48 928 A1, the rail stands an a substantially C-shaped elastic mounting profile which fits round the sides of the foot of the rail and which rests on a sleeper composed of concrete. This arrangement is intended to ensure low-noise, damped running of trams on the rail. To hold down the rail, use is made of clamping profiles which are fixed in place by means of respective fastening screws screwed into the sleeper. The clamping profiles have in this case a fastening portion which is supported on the sleeper and on which there is integrally formed a projection which, in the fitted state, presses against the free upper side of the foot of the rail. To make it possible for the gauge to be adjusted at the same time, there are provided in addition in this known system, trapezoidal gauge-defining profiles which are displaceable at lateral gauge-defining edges of the rail supports of the sleeper and which have slotted holes parallel to the longitudinal direction of the rails for the fastening screws. In this way, the gauge-defining profiles form guides in the transverse direction which are adjustable in the horizontal direction for their respective associated rails.
Something which has proved to be a problem in the practical use of rail fastenings of the kind explained above is the fact that the fastening screws come loose, meaning that the fastening requires maintenance after operating for only a comparatively short period.